/SimpleWebDiscoveryInspector.cs

// Copyright 2011 Microsoft Corporation

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.





using System;

using System.Collections.Generic;

using System.ServiceModel;

using System.ServiceModel.Channels;

using System.ServiceModel.Description;

using System.ServiceModel.Dispatcher;

using System.Text;

using System.Xml;



namespace Microsoft.Data.Services.Client

{

    class SimpleWebDiscoveryInspector : IDispatchMessageInspector

    {

        // Assume utf-8, note that Data Services supports

        // charset negotation, so this needs to be more

        // sophisticated (and per-request) if clients will 

        // use multiple charsest

        private static Encoding encoding = Encoding.UTF8;



        private IDictionary<string, string[]> endpoints;



        private const string swdPath = "/$wellknown/simple-web-discovery";



        public SimpleWebDiscoveryInspector(IDictionary<string, string[]> endpoints)

            : base()

        {

            this.endpoints = endpoints;

        }



        #region IDispatchMessageInspector Members



        public object AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, IClientChannel channel, InstanceContext instanceContext)

        {

            if (request.Properties.ContainsKey("UriTemplateMatchResults"))

            {

                HttpRequestMessageProperty httpmsg = (HttpRequestMessageProperty)request.Properties[HttpRequestMessageProperty.Name];

                UriTemplateMatch match = (UriTemplateMatch)request.Properties["UriTemplateMatchResults"];



                string pathAfterSvc = match.RequestUri.AbsolutePath.Replace(match.BaseUri.AbsolutePath, "");

                if (pathAfterSvc.Equals(swdPath))

                {

                    httpmsg.Headers["Accept"] = "application/json";



                    string service = match.QueryParameters["service"];

                    if (this.endpoints.ContainsKey(service))

                    {

                        return this.endpoints[service];

                    }

                }

            }

            return null;

        }



        public void BeforeSendReply(ref System.ServiceModel.Channels.Message reply, object correlationState)

        {

            if (correlationState != null && correlationState is string[])

            {

                string[] addresses = correlationState as string[];

                string content = "{ \"locations\" : " + ToJsonArray(addresses) + " }";



                Message newreply = Message.CreateMessage(MessageVersion.None, "", new Writer(content));

                newreply.Properties["WebBodyFormatMessageProperty"] = new WebBodyFormatMessageProperty(WebContentFormat.Raw);



                HttpResponseMessageProperty prop = (HttpResponseMessageProperty)reply.Properties["httpResponse"];

                prop.StatusCode = System.Net.HttpStatusCode.OK;

                newreply.Properties["httpResponse"] = prop;



                reply = newreply;

            }

        }



        private string ToJsonArray(string[] array)

        {

            string content = "[ ";

            if (array.Length > 0)

            {

                content += "\"" + array[0] + "\"";

                for (int i = 1; i < array.Length; ++i)

                {

                    content += ", \"" + array[i] + "\"";

                }

            }

            return content + " ]";

        }

        

        #endregion



        class Writer : BodyWriter

        {

            private string content;



            public Writer(string content)

                : base(false)

            {

                this.content = content;

            }



            protected override void OnWriteBodyContents(XmlDictionaryWriter writer)

            {

                writer.WriteStartElement("Binary");

                byte[] buffer = SimpleWebDiscoveryInspector.encoding.GetBytes(this.content);

                writer.WriteBase64(buffer, 0, buffer.Length);

                writer.WriteEndElement();

            }

        }

    }



    // Simply apply this attribute to a DataService-derived class to allow

    // simple web discovery support in that service

    [AttributeUsage(AttributeTargets.Class)]

    public class SimpleWebDiscoveryBehaviorAttribute : Attribute, IServiceBehavior

    {

        private IDictionary<string, string[]> endpoints;



        public SimpleWebDiscoveryBehaviorAttribute(Type type) : base()

        {

            Endpoints endpointDictionary = (type.GetConstructor(new Type[] { }).Invoke(new object[] { })) as Endpoints;

            if (endpointDictionary == null)

            {

                throw new ArgumentException("Argument must be a subclass of the Endpoints class.");

            }

            endpoints = new Dictionary<string, string[]>();

            foreach (KeyValuePair<string, List<string>> p in endpointDictionary.EndpointDictionary)

            {

                this.endpoints[p.Key] = p.Value.ToArray();

            }

        }



        #region IServiceBehavior Members



        void IServiceBehavior.AddBindingParameters(

            ServiceDescription serviceDescription,

            ServiceHostBase serviceHostBase,

            System.Collections.ObjectModel.Collection<ServiceEndpoint> endpoints,

            System.ServiceModel.Channels.BindingParameterCollection bindingParameters)

        {

        }



        void IServiceBehavior.ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)

        {

            foreach (ChannelDispatcher cd in serviceHostBase.ChannelDispatchers)

            {

                foreach (EndpointDispatcher ed in cd.Endpoints)

                {

                    ed.DispatchRuntime.MessageInspectors.Add(new SimpleWebDiscoveryInspector(this.endpoints));

                }

            }

        }



        void IServiceBehavior.Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)

        {

        }



        #endregion

    }



}